Field of the Invention
The present invention relates to a solid electrolyte CO2 sensor and a manufacturing method thereof, and more particularly, to a solid electrolyte CO2 sensor in which the joining and sealing of a reference electrode by a reaction caused by a heat treatment between a substrate and a solid electrolyte allows the reference electrode to suppress a side reaction such as adsorption of moisture, and a manufacturing method thereof.
Description of Related Art
Automobiles are a means of transportation, which is essential for human life, and make life richer and more convenient. Recently, automobiles have become more high-end, various options have been added, and among them, technologies for constructing a safe driving system of the automobile have been studied. As efforts to create a comfortable environment for safe driving during the driving have been accelerated, alternatives such as replacement of components applied to seats of vehicles with materials which emit less carcinogens have been suggested, and among them, interests in the quality of air inside the vehicle are increasing and much attention has been paid to carbon dioxide (CO2). Carbon dioxide affects humans in a sealed space in various ways, is a factor affecting driving, and is responsible for reducing the driver's brain activities and causing drowsy driving. Accordingly, the real-time monitoring of the concentration of carbon dioxide for safe driving of vehicles and the function of monitoring and suppressing the environment for causing drowsy driving in real time in connection with the air conditioning system of vehicles in addition to that have drawn attention. Accordingly, there is a need for a sensor for measuring the concentration of carbon dioxide, and as a solution to the need, optical (non-dispersive infrared: NDIR) sensors, semiconductor-type gas sensors, and home or universal sensors in a solid electrolyte system have been suggested.
Meanwhile, carbon dioxide is a gas whose concentration is difficult to measure as a chemically very stable gas in the atmosphere, the optical sensor is most frequently used as a sensor for sensing the carbon dioxide, and this system is a system in which light with a specific wavelength of emitted laser is absorbed by carbon dioxide in the air, the amount of intensity of light reduced is sensed, and the amount of carbon dioxide is measured. This device has an advantage in that selectivity, sensitivity and reproducibility are excellent, but has problems in that a hermetically sealed space is required for measurement, and the volume is large and the weight is very heavy due to the physical sizes of constituent elements and filters. In particular, since the driving part and the measurement device are very expensive and the configuration of the processing part for control is complex, the price of the overall measurement equipment is definitely high, and accordingly, this device fails to be widely utilized even though the use thereof is very diverse.
As another system for measuring the concentration of carbon dioxide, a semiconductor-type gas sensor using a semiconductor compound such as SnO2 or TiO2 is used, and uses a principle of measuring the concentration of the gas through a change in resistance displayed when gas particles are adsorbed on the surface of the semiconductor compound. In this case, there is an advantage in that a sensor in the form of a thin film-type device can be manufactured, but there is also a disadvantage in that the gas selectivity significantly deteriorates because it is difficult to tell different gas particles to be adsorbed apart, and accordingly, it is difficult to use the semiconductor-type gas sensor as a device to select and measure only carbon dioxide.
The home or universal sensor in a solid electrolyte system in the related art has a limitation in use for an automobile because sensor signals are affected by reactive gases such as moisture, and the durability deteriorates. Therefore, there is a need for developing a solid electrolyte CO2 sensor which may overcome the limitation of the universal sensor in a solid electrolyte system.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.